1. Field of the Invention
The present invention generally relates to seismic data acquisition, and more specifically to ocean bottom seismic data acquisition systems.
2. Description of the Related Art
In conventional marine seismic surveying, a vessel tows a seismic source, such as an airgun array, that periodically emits acoustic energy into the water to penetrate the seabed. Sensors, such as hydrophones, geophones, and accelerometers may be housed in sensor units at sensor nodes periodically spaced along the length of an ocean bottom cable (OBC) resting on the seabed. Alternatively, a plurality of autonomous sensor nodes, each comprising one or more seismic sensors may be deployed on the seabed. The sensors of the sensor node are configured to sense acoustic energy reflected off boundaries between layers in geologic formations. Hydrophones detect acoustic pressure variations; geophones and accelerometers, which are both motion sensors, sense particle motion caused by the reflected seismic energy. Signals from these kinds of sensors are used to map the geologic formations.
The power required to operate the sensor nodes may be provided via batteries and/or power generators. For example, in OBC systems, the cable may be connected to a surface buoy or a seismic vessel comprising a generator, e.g., a diesel generator. The generator may provide power for operating the sensors either directly or indirectly (e.g., via chargeable batteries). In autonomous sensor node based system, rechargeable batteries may be included in each node to power the node.